This invention relates to fuel tanks for automobiles, and in particular, to plastic multilayered fuel tanks that prevent hydrocarbon fuel vapours from escaping to the environment.
Due to environmental concerns relating to the emission of hydrocarbon vapours from fuel tank systems in motor vehicles, the Government of the United States of America, amongst others, is now demanding that motor vehicle fuel tank systems built as of 2003 provide virtually no hydrocarbon vapour emissions to the environment. Moreover, the specifications will require that the fuel tanks maintain this low level of emissions during the lifetime of the motor vehicle.
Presently, a majority of motor vehicle fuel tank systems made are of plastic, however, one drawback is that they tend emit some amount of hydrocarbon fuel vapours to the environment. Most of these hydrocarbon vapour emissions occur through the fuel tank""s hoses, connectors, seals, tank seams, etc. generally located at the top of the fuel tanks. FIG. 1 is a schematic sketch showing in general the emission of hydrocarbon vapours from these locations on the prior art fuel tanks.
The prior art has several examples of fuel tanks that include means for trapping liquid or vapour fuel. However, none of the prior art fuel tanks are designed and intended to prevent or minimize the leakage of hydrocarbon vapour to the environment.
U.S. Pat. No. 3,804,291 to Fricker discloses a venting and pressure release device for fuel tanks, in which a container (preferably made of synthetic plastic material) is provided on the inside of the fuel tank within the highest area and located at least partially above the maximum filling height. Fuel vapours in the fuel tank travel through a number of channels between the upper tank wall and the upper wall of the container to a dome structure mounted on or arranged on the top of the fuel tank before exiting the tank via another series of gaps and channels and a vent pipe. The dome may also be made in one piece with the upper container parts or mounted thereon.
Fricker also teaches a tank principle in which only one, possibly rigid line for the venting of the tank has to be extended to the outside so that connecting places located outside of the tank are eliminated.
U.S. Pat. No. 3,917,109 issued to MacDonald discloses a vent system that minimizes the possibility of vapour leakage to the atmosphere. It discloses a fuel tank for motor vehicles having a dome-shaped portion rising above the upper surface of the tank. The dome portion provides for a vapour space and in which a liquid-vapour separator is mounted. The separator is an enclosed container that serves as a locus for the collection of those vapours by flow thereof into a vapour vent conduit in addition to being a device for separating vapours from liquid fuel and acting as a baffle to prevent liquid fuel carryover.
MacDonald teaches that fuel vapours exit the fuel tank and the separator by entering a single vapour vent conduit that communicates between the interior of the separator and the exterior of the fuel tank. One end of the vapour vent conduit is extended into the doomed portion and the other end is extended to a charcoal canister and ultimately to an engine or any appropriate vapour receiving means on the motor vehicle.
U.S. Pat. No. 4,714,171 issued to Sasaki et al. discloses a vent system for venting fuel vapour from a fuel tank of a motor vehicle. The Sasaki vent system comprises a fuel tank constructed of moulded plastics with a depressed portion which protrudes into a vapour chamber defined at an upper portion of the interior of the fuel tank; a structure of moulded plastic which defines an enclosed chamber at a position above the maximum level of fuel in the fuel tank and means for fluid communication; namely, pipes, connectors and tubing.
Fuel vapours produced in the fuel tank are led into the enclosed chamber and the vapours are then led to a canister and trapped by the same. The enclosed chamber may be a deepened recess formed in an upward swelled portion of the fuel tank, or it may be the chamber of a separate vapour separator of moulded plastic which is either detachably mounted on the fuel tank or mounted on the upper wall of the fuel tank. The enclosed chamber may also have an opening having a lid sealingly attached to it.
U.S. Pat. No. 4,836,402 issued to Sasaki discloses a vent system for venting fuel vapour from a fuel tank of an automotive vehicle. The Sasaki fuel tank has a top wall, a vacant space between the top wall and the surface of fuel filled, and a separator chamber in the vacant space having a number of vent pipes for venting fuel vapour from the fuel tank. The fuel vapour is first drawn through the vent pipes into the separator chamber and then to a carbon canister outside the fuel tank.
U.S. Pat. No. 5,398,839 issued to Kyeln discloses a fuel tank encapsulated by an outer shell (preferably made of molded plastic material), and having a space between the outer shell and the fuel tank. Any liquid fuel leaking from the fuel tank is trapped by fuel absorbent material filling the space between the fuel tank and the outer shell and prevented from escaping to the environment. The Kyeln fuel tank may also be connected to a vapour recovery system. Kyeln also discloses an injection moulding apparatus for making such a fuel tank.
The present invention addresses these environmental problems associated with plastic fuel tanks, and also other problems as described below. Accordingly, it is an object of one aspect of the present invention to provide a fuel tank in which hydrocarbon vapour leaks from the tank body are contained and encapsulated within a separate vapour chamber. This additional vapour collection chamber of the fuel tank traps vapours instead of being released into the environment. In a preferred embodiment, the charcoal canister filter on the fuel tank is operatively connected to the vapour chamber for directing the leaked hydrocarbon vapours to the engine for combustion. It is another object of another aspect of the present invention to provide a method of preventing vapour fuel from escaping from a motor vehicle fuel tank to the environment.
Accordingly, in one aspect of the present invention, there is provided a multilayered fuel tank for a motor vehicle, comprising:
(a) a fuel tank body for holding liquid and vapour fuel comprising a bottom wall, side walls and a top wall;
(b) a plurality of fuel tank components located on the top wall and seams located on the side walls; and
(c) a tank cover connected to the fuel tank body and defining a vapour collection chamber, the tank cover encapsulating the top wall and the fuel tank components and seams thereby trapping any fuel vapours that escape from the tank body, the fuel tank components and the seams.
In a second aspect of the present invention, there is provided an accessory for a motor vehicle fuel tank comprising a bottom wall, side walls, a top wall, seams and a plurality of fuel tank components located on the top wall, the accessory comprising:
a tank cover for connection to the fuel tank to define a vapour collection chamber, the tank cover protecting and encapsulating the top wall, the fuel tank components and the seams thereby trapping any fuel vapours that may escape from the tank body, the fuel tank components and the seams during use of the fuel tank.
In a third aspect of the present invention, there is provided a method of making a multilayered fuel tank for preventing the escape of fuel vapour to the environment, the method comprising:
(a) providing a fuel tank body for holding liquid fuel and vapour comprising a bottom wall, side walls and a top wall and a plurality of fuel tank components located on the top wall and seams located on the side walls; and
(b) connecting a tank cover to the fuel tank body, the tank cover defining a vapour collection chamber and encapsulating the top wall and the fuel tank components and seams thereby trapping any fuel vapours that may escape from the tank body, the fuel tank components and the seams when in use.
In a further embodiment of the present invention, method is provided of preventing fuel vapour from escaping from a fuel tank for motor vehicles to the environment, comprising:
(a) providing a fuel tank body for holding liquid fuel and vapour comprising a bottom wall, side walls and a top wall, and a plurality of fuel tank components located on the top wall and seams located on the side walls;
(b) connecting a tank cover to the fuel tank body, the tank cover defining a vapour collection chamber and encapsulating the top wall and the fuel tank components and seams thereby trapping any fuel vapours that may escape from the tank body, the fuel tank components and the seams; and
(c) directing the trapped fuel vapours through a charcoal cannister filter to the motor vehicle engine for combustion.